1. Technical Field
This application relates to manufacturing systems and methods in general, and more specifically, to methods and systems for the automated placement of flexible sleeves on elongated mandrels.
2. Related Art
The manufacture of composite structures, e.g., composite-bodied aircraft, involves the fabrication of structural components comprising matrices of a plastic, e.g., a thermosetting resin, within which reinforcing fibers, e.g., carbon or glass fibers, are embedded.
Some such structural components, e.g., door surrounds, stringers, spars, and similar long/thin geometries, can be fabricated by placing a flexible sleeve, e.g., a braided glass or carbon fiber sleeve, over an elongated mandrel, and then encapsulating the sleeve within a layer of a liquid plastic, e.g., a thermosetting resin, which is subsequently cured, partially or fully. In some embodiments, the sleeve can then be removed from the mandrel or vice-versa for subsequent processing, and in others, the mandrel, which can be solid or tubular, can remain within the sleeve and comprise an integral, “core” portion of the finished product.
Sleeves, and in particular, bi-axially braided sleeves, are intrinsically difficult to install onto elongated mandrels manually due to their material properties, in which a lack of longitudinal tension can result in an undesirable increase in the diameter of the sleeve. The issue is exacerbated by the requirement that material placement be uniformly smooth in order to avoid wrinkles in the finished product. Consequently, manual processes tend to be slow and result in substantial variability in the finished product quality. Once the length of the sleeve exceeds a certain length, manual handling and loading of the sleeve becomes very difficult, unless automation methods and apparatus are employed. An example of this is in the case of long (>100 in.) aircraft stiffeners, such as fuselage and wing skin stiffeners and vent stringers. During manual handling, there is the potential for the introduction of Foreign Object Debris (FOD) and the material can be easily damaged. Additionally, there are Environmental Health and Safety (EHS) issues associated with the handling of, e.g., glass and carbon fibers, such as skin and respiratory irritation.
Accordingly, there is a long-felt but as yet unsatisfied need in the industry for systems and methods for the automated placing of flexible sleeves on elongated mandrels that overcome the foregoing and other problems of the conventional manual placement techniques.